With a high-speed liquid chromatograph, for example, it is necessary to switch between flow paths to be connected under the condition of high-pressure delivery of a mobile phase. As a flow path switching valve used under such condition of high pressure, a rotary switching valve including a stator having a plurality of ports for connecting flow paths, and a rotor having a surface that comes into close contact with the stator and a switching groove, on the surface, for communicating two ports of the stator (see Patent Document 1) may be used. The rotary switching valve switches the flow paths to be connected, by switching the ports to be communicated by rotating the rotor while keeping the flat surfaces of the stator and the rotor in close contact with each other.
An example of the structure of the rotary switching valve is shown in FIG. 4.
This switching valve has a cylindrical base 42 forming a lower portion of a housing and a stator 40 forming an upper portion of the housing fixed to each other by a plurality of screws 44. A plurality of ports 46 for connecting flow paths are provided at an upper surface of the stator 40. Each port 46 is open to a lower surface 41 of the stator 40 which is an upper flat surface inside the housing. A rotor 10 is accommodated inside the base 42. A switching groove 14 for communicating the plurality of ports 46 of the stator 40 is provided on the flat surface of the rotor 10, on the side of the stator 40. The flat surface of the rotor 10, on the side of the stator 40, is in close contact with the lower surface 41 of the stator 40.
The rotor 10 is held by a rotor holding unit 8, and the rotor holding unit 8 is provided at a tip end of a shaft 12. The shaft 12 is extended outside through a hole at a center portion of the base 42. A rotating mechanism (not shown) for rotating the shaft 12 is provided outside the base 42. The rotor holding unit 8 is rotated by the rotation of the shaft 12, and the rotor 10 is then rotated. When the rotor 10 is rotated, the position of the switching groove 14 changes, and the ports 46 of the stator 40 to be connected are switched.
A ring bearing 20 for suppressing movement of the shaft 12 is arranged at a lower portion inside the base 42. A bearing 22 for suppressing shaky rotation of the rotor holding unit 8 is inserted between an outer circumferential surface of the rotor holding unit 8 and an inner circumferential surface of the base 42. A spring 18 is inserted between the rotor holding unit 8 and the bearing 20 in a compressed manner. The rotor holding unit 8 is biased toward the stator 40 by the elastic force of the spring 18, and the rotor 10 is thereby pressed against the lower surface of the stator 40. The liquid tightness between the rotor 10 and the stator 40 is thereby enhanced, and liquid leakage from the switching groove 14 of the rotor 10 is prevented.